# UBCO-PSYO271 Ch. 1: Study of Statistics

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### statistics

A set of procedures for organizing, describing, and interpreting quantitative information and drawing related inferences and conclusions.

### variability

The fact that measurement values obtained in a study differ from one another, despite each subject being assessed under the same circumstances.

### individual differences

How subjects display differences in behaviour. This is the first major source of variability in psychological measurements.

### measurement error

Referring to how measurement values may not provide accurate descriptions due to flaws in how the values are obtained (such as ambiguous question wording). This is the second major source of variability in psychological measurements.

### statistical unreliability

Referring to how an individual subject may provide different measurement scores on any given trial. This is the third major source of variability in psychological measurements.

### descriptive statistics

Procedures for organizing, summarizing and describing data.

### inferential statistics

Methods for making inferences about a arger group of individuals on the basis f data actually collected on a much smaller group.

### measurement

The orderly assignment of a numerical value to a characteristic.

### placebo

A supposed treatment that actually provides no effect upon a subject, except those caused by the subject's belief that the treatment works.

### population

The complete set of individuals of interest in a study.

### sample

A number of subjects selected from a population who are actually examined in a study.

### probability

The percentage chance than an expected result could occur. In psychological measurements, this is often used to refer to the chance that an observed behaviour occurs due to simple variability.

### scale of measurement

The ordered set of possible numbers that may be obtained by the measurement process.

### rank order

An ordering system that arranges the values being studied according to their relative differences in magnitude, such as from smallest to largest.

### categorization

Assigning values in a measurement scale into classes or groups.

### magnitude

The relative size of an value compared to other values being measured.

### equal intervals

Referring to a the magnitude of a value on a scale being the same regardless of where on the scale that the value falls.

### absolute zero point

A value at which nothing at all of the attribute being measured exists; for example, having zero height.

### nominal scale

A scale which classifies items into mutually exclusive groups that do not bear any magnitude relationships to one another.

### ordinal scale

A scale in which magnitude is measured without utilizing equal intervals or an absolute zero point, such as in a rank order.

### interval scale

A scale which possesses the properties of magnitude and equal intervals but not an absolute zero point

### ratio scale

A scale of measurement which possess magnitude, equal intervals, and an absolute zero point.

### variable

A general characteristic being measured on a set of people, objects, or events, the members of which may take on different values.

### constant

A quantity that does not change its value within a given context.

### discrete variable

A variable that can assume only a countable number of values between any two points.

### continuous variable

A variable which can assume a potentially infinite number of values between any two points on a measurement scale.

### real limit

The points falling one-half measurement unit and one-half measurement unit below a number (ex. 32.5 and 33.5 for 33).

### distribution

An arrangement of values of a variable showing their observed or theoretical frequency of occurrence .

### Σ (sigma)

A symbol used to refer to summation, or adding together all of the designated values together.

### cross product

A value formed by multiplying a subject's first score by their second score.

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